The centriole/basal body (CBB) is a widely conserved eukaryotic organelle that plays essential role in the cell division and sensing. Despite such significance, the mechanism of CBB assembly is not fully elucidated. To add to our understanding of CBB assembly, we isolated a temperature sensitive mutant, or452ts, which exhibited centrosome duplication defects and identified the causal gene T07C4.10 using whole genome sequencing. We also used CRISPR to generate a likely null allele, or1942. The affected gene has weak homology to Chibby family protein, which is widely conserved among eukaryotes, including humans. Chibby is known to be involved in basal body formation in fly, frog and human. However, the role during cell division has not been reported. Interestingly, a GFP-tagged Ce-Chibby protein exclusively localizes to the centriole, suggesting that it is a new essential centriolar gene. In C. elegans, five core centriole proteins—SPD-2, ZYG-1, SAS-5, SAS-6 and SAS-4—are known to localize to centrioles and function sequentially to regulate centriole duplication and biogenesis. SPD-2 is the first protein recruited to the newly formed centriole after fertilization and is required for the centriolar localization of the other core proteins. To determine the timing of Ce-Chibby localization to the newly formed centriole, we analyzed maternal GFP::Chibby localization after mating with non-GFP males and found that GFP::Chibby started to localize to the centriole as early as the SPD-2 protein. Moreover, in spd-2(RNAi) animals, maternal GFP::Chibby still localized to the centriole, suggesting that the centriolar localization of Ce-Chibby is SPD-2 independent. In contrast, SPD-2 centriolar localization was delayed in a chibby(null) mutant, suggesting that Ce-Chibby regulates proper SPD-2 localization. Interestingly, Ce-Chibby interacts with SPD-2 by the yeast two-hybrid assay through the C-terminal 263 amino acids that include a conserved 24 amino acid motif. Finally, wild-type males can partially rescue embryonic viability when mated with homozygous chibby(-) mutants, suggesting that chibby may have both maternal and paternal contributions. In summary, we have identified a C. elegans Chibby-like protein which functions in the most upstream step of the centriole biogenesis to promote SPD-2 centriolar recruitment, possibly through a physical interaction.
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